How To Choose The Correct Bike Size: Road Bike Edition [With Video Guide]

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Road cycling is a lot of fun, and ripping up the tarmac is a great way to stay in shape and enjoy the outdoors.

Being on the correct bike size is vital when it comes to road cycling. It’s very easy to overlook, and many cyclists get it wrong – and suffer the consequences!

Road bikes come in all different designs, and bike size changes from one bike manufacturer to another. Finding the correct size for you can be quite challenging, and it’s something many cyclists struggle with. 

This article will tell you everything you need to know when picking the correct size road bike. We’ll be covering:

  • 3 Reasons Why The Correct Road Bike Size Is Essential
  • Understanding Different Styles Of Road Bike
  • 3 Key Road Bike Size Measurements
  • Our Proven Methods To Pick The Correct Size Bike For You
  • “Sizing Up” Vs. “Sizing Down”
  • Robbie’s Video Guide: Choosing The Right Road Bike Size

Let’s dive in!

A Yoeleo R12 road bike in a wall stand.

3 Reasons Why The Correct Road Bike Size Is Essential

When I first started cycling, I bought a 52 cm Claud Butler road bike. This would have been fine if I was 5’8″, but being 6 ft, it made my cycling experience pretty awful!

Here are the three key factors I learned the hard way about riding the wrong bike size in my early years as a professional endurance cyclist:

#1. Comfort 

The biggest and most important thing when it comes to having the correct size bike is comfort.

If you are on a bike too big for you, it’s going to stretch you out. If you’re on a bike too small for you, it will tighten you up too much. 

#2. Performance 

If you’re riding a bike that is too big or small for you, it won’t perform right.

It won’t handle the same, and the modifications you will need to make for comfort will mess up your geometry – plus it will be harder to cycle efficiently. 

#3. Injury Prevention

If you are going to want to ride decent miles and don’t want injuries, you really have to be on the right bike frame size for you.

The wrong bike frame size and long rides are a recipe for disaster, and I personally suffered countless unnecessary injuries on my first bike because I used the wrong size. 

The sizing number on a road bike down tube.

Understanding Different Styles Of Road Bike

It’s important to understand that road bikes come in different styles, which can affect their sizing.

Here’s what you need to know:

  • Racing Road Bike: Aggressive geometry, stiff, lightweight frames, and a small headtube.
  • Endurance Road Bike: Relaxed geometry, forgiving frames, tall headtube.
  • Aero Road Bike: Aggressive geometry, stiff aerodynamic frame, small-to-medium headtube.

The style of the bike will change how the bike is sized. For example, a racing bike will have a smaller head tube compared to an endurance bike. An endurance road bike might have a smaller seat tube than an aero road bike. 

This means when it comes to looking for the right size for you, the bike could have completely different measurements compared to what you are used to. It doesn’t mean it won’t fit you. 

It’s important to understand that all road bikes are not the same, and it’s not always as simple as just chucking out a measuring tape and doing some basic measurements when you need to find the right size bike for you.

3 Key Road Bike Size Measurements

When it comes to bike sizing, there are certain measurements that are key to manufacturers getting the correct sizes.

Here’s what you need to know:

#1. Top Tube 

A cyclist showing how to measure the top tube of a road bike.

This is the distance from the top tube to the seat tube, measured horizontally.

This will typically be measured as anywhere from 46 cm to 62 cm. A longer top tube stretches the rider out, making them more aerodynamic. A shorter top tube gives a more comfortable riding position.

The top tube is the most important measurement, as it is the one used most often to define bike frame size.

For example, if a bike is described as being “58 cm” or “size 58”, that means it has a 58 cm top tube.

#2. Seat Tube

A cyclist showing how to measure a seat tube of a road bike.

The seat tube measurement is the distance between the center of the crankset to the top of the seat tube (where the seat post emerges).

This can greatly differ depending on the type of bike, and many bikes come with extra-long seat tubes for flexibility.

#3. Head Tube

A cyclist showing how to measure a head tube on a road bike.

Then we have the head tube. This is the size of the part of the frame which holds the forks in place.

A longer head tube works for taller riders and can give a more upright riding position. 

Our Proven Methods To Pick The Correct Size Bike For You

When it comes to finding the correct size bike for you, there are a few different avenues you can go down. Here are our expert-proven methods:

Generic Road Bike Size Chart

A road bike size chart showing typical measurements for road bike frame sizes as described by manufacturers.
Road Bike Size Chart

The first place you can start is with this generic road bike size chart.

This is going to give you very general information and doesn’t take bike type into account, but can come in handy as a reference point if you’re looking at a wide range of bikes.

This is our bike frame size chart, and although it will give you a good indication of what road bike size you need, bear in mind that it’s only a rough guide.

The type of road bike makes such a big difference, so this bike frame size chart should be regarded as a starting point, not a definitive guide. Note that there’s some overlap between different sizes!

Manufacturers Guidelines

The next place we recommend looking when you’ve honed in on a particular model is the manufacturer’s guidelines.

Typically, on the manufacturer’s website, you can find guidelines on what size you should have for your height, inseam, or other measurement.

Brands such as Specialized, Trek, and Canyon label their sizes from XS all the way through to XXL. It’s important to understand that a large road bike in one brand could be perfect for you, but with another brand, it could be completely wrong. 

This is probably the easiest way to find the correct size road bike for you. After, we recommend heading to a bike fitter to get them to perfect the fit for your body.

Use Measurements

Measuring a top tube of a classic road bike.

Another route you can go down is using the bike’s measurements to see if it’s right for you.

This is a bit more challenging to do, as you have to take into account the types of bikes we spoke about earlier and the design of the bike. 

By taking measurements of the current bike you are using, you will be able to match up the new bike. This is a more challenging way to go, but these measurements will tell you a lot about how a bike will ride, and you can tell quickly if the bike will work for your style of riding.

A crank with a tape measure across it measuring the seat tube.

Test Ride

Regardless of which method you’re using, the most important step is a test ride! Many bike shops will have demo bikes that you can take out and use.

Finding a shop with the bike you’re looking for and asking if you can test it is a great idea. If not, there’s a big open cycling community who are generally very happy to help. I have let many people ride bikes of mine to see if it will be right for them. 

A rear light on a classic road bike.

See A Bike Fitter

Many cyclists think that a bike fitter is only used when you already have the bike, but they would be wrong. Bike fitters will commonly have rigs where they can let you ride, and you can have a fit before buying a bike. 

This fit will not only tell you exactly how tall your saddle height should be, where your reach should be, and even the correct crank length, but it will also tell you what bikes will work for you and what won’t.

In my experience working as a professional bike fitter, I have found a very common problem for many cyclists is they were simply on the wrong sized bike, and most of the time, they have just purchased it online, or it was reduced at a bike shop. 

Unfortunately, they would never get a perfect fit. However much adjusting you do, a poorly sized frame will never be quite right.

A bike fitter will be able to advise you exactly what size to buy depending on the measurements they have made for you, and although it’s a lot to go through before getting a bike, it’s often worth it. 

We highly recommend a bike fit whatever size bike you are on. It’s a process that hugely improves comfort and pedaling efficiency.

A double chainset on a classic road bike.

“Sizing Up” Vs. “Sizing Down”

As humans, we are all different shapes and sizes.

This can make it difficult when it comes to getting the right size bike for you, as you might fall right in between two sizes. This is an issue I have faced many times – both as a bike fitter and when finding frames for myself.

For the seat tube, I typically require a larger size, but for the top tube, I generally need a medium or medium large. So when I find myself in this situation, knowing what I need to do can be challenging. Do I size up or size down?

Here’s what I recommend:

When You Should Consider “Sizing Up”

If I am looking for a bike for comfort and endurance, then I personally tend to size up.

This is because the taller headtube will offer a more relaxed position, and I will get more comfort from that. To compensate, I will bring the seat forward, and reduce the stem length. 

When You Should Consider “Sizing Down”

If I was using a bike for racing or I was time trialing, I would consider dropping to the smaller size.

It would offer a much more aggressive position and be slightly lighter. Although it wouldn’t offer comfort, it would offer speed. I’d have to push the seat back and lengthen the stem in this case to compensate.

Robbie’s Video Guide: Choosing The Right Road Bike Size

Check out the BikeTips YouTube Channel here for walk-through bike maintenance guides and more!

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Robbie has traveled the globe as an endurance athlete and bikepacker, breaking world records and competing in international ultra-cycling events such as the BikingMan series and the Transcontinental Race. He's also worked as an ambassador for some of the industry's leading names, including Shimano and Ritchey. If Robbie's not on a bike, he's either fixing them or out walking with his dog!

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